WPF中Button的SourceUpdated事件未触发，绑定源变更未同步至内容

问题代码 #

XAML文件 #

<Window x:Class="notify_on_source_updated.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:notify_on_source_updated"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
    <Button x:Name="myButton" Click="myButton_Click" />
</Window>

代码后置文件 #

namespace notify_on_source_updated
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        public string SourceText {get; set;}
        
        public MainWindow()
        {
            InitializeComponent();
            SourceText = "test";
            Binding binding = new Binding();

            binding.Source = SourceText;
            binding.NotifyOnSourceUpdated=true;
            
            myButton.SourceUpdated += myButton_SourceUpdated;
            myButton.SetBinding(ContentControl.ContentProperty, binding);
        }

        private void myButton_Click(object sender, RoutedEventArgs e)
        {
            SourceText = "changed";
        }

        private void myButton_SourceUpdated(object sender, DataTransferEventArgs e)
        {
            MessageBox.Show("Updated!");
        }
    }
}

疑惑与解答 #

1. 点击按钮后Button Content未更新为"changed" #

原因：SourceText是普通CLR属性，未实现INotifyPropertyChanged接口。WPF的数据绑定依赖属性变更通知同步UI，当属性值修改时，如果没有触发PropertyChanged事件，WPF无法感知值的变化，因此不会更新UI。

2. SourceUpdated事件从未触发 #

原因：你混淆了SourceUpdated事件的触发逻辑：

• SourceUpdated仅在目标控件的值回传给源对象时触发（比如TwoWay绑定下，用户修改TextBox的Text，值同步到源属性的场景）。
• 你的绑定是默认的OneWay模式（仅源→目标同步），且操作是手动修改源属性值，这种场景下不会触发SourceUpdated。若要监听源属性更新到目标的动作，应该使用TargetUpdated事件，并设置binding.NotifyOnTargetUpdated=true。

修正方案 #

步骤1：实现INotifyPropertyChanged接口 #

让窗口类实现接口，给SourceText添加属性变更通知：

namespace notify_on_source_updated
{
    public partial class MainWindow : Window, INotifyPropertyChanged
    {
        private string _sourceText;
        public string SourceText
        {
            get => _sourceText;
            set
            {
                if (_sourceText != value)
                {
                    _sourceText = value;
                    OnPropertyChanged(nameof(SourceText));
                }
            }
        }

        public event PropertyChangedEventHandler PropertyChanged;
        protected void OnPropertyChanged(string propertyName)
        {
            PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));
        }

        public MainWindow()
        {
            InitializeComponent();
            SourceText = "test";
            // 绑定源改为当前窗口实例，而非直接绑定SourceText字段
            Binding binding = new Binding(nameof(SourceText))
            {
                Source = this,
                // 启用目标更新通知（源→目标同步时触发）
                NotifyOnTargetUpdated = true
            };
            
            // 绑定TargetUpdated事件
            myButton.TargetUpdated += MyButton_TargetUpdated;
            myButton.SetBinding(ContentControl.ContentProperty, binding);
        }

        private void myButton_Click(object sender, RoutedEventArgs e)
        {
            SourceText = "changed";
        }

        private void MyButton_TargetUpdated(object sender, DataTransferEventArgs e)
        {
            MessageBox.Show("目标已更新！");
        }
    }
}

步骤2：明确绑定方向与事件的对应关系 #

• OneWay绑定：源→目标，源变化时更新目标，对应TargetUpdated事件（需设置NotifyOnTargetUpdated=true）。
• TwoWay绑定：源↔目标，目标变化回传源时触发SourceUpdated事件（需设置NotifyOnSourceUpdated=true），源变化更新目标时触发TargetUpdated。

若要测试SourceUpdated，可使用TextBox的TwoWay绑定示例：

// 构造函数中替换绑定逻辑
TextBox textBox = new TextBox();
Binding binding = new Binding(nameof(SourceText))
{
    Source = this,
    Mode = BindingMode.TwoWay,
    NotifyOnSourceUpdated = true
};
textBox.SourceUpdated += TextBox_SourceUpdated;
textBox.SetBinding(TextBox.TextProperty, binding);
// 将textBox添加到窗口布局
this.Content = textBox;

此时在TextBox中输入文本，值同步到SourceText时会触发SourceUpdated事件。

内容的提问来源于stack exchange，提问作者user32882